1. Technical Field
This invention relates to a method of extracting polysaccharide. In particular, the invention provides a technique whereby the crude polysaccharide can be extracted by microwave-assisted from Artemisia sphaerocephala seed de-oiling dregs.
2. Background
Artemisia sphaerocephala Krasch (Asteraceae) is widely distributed in desert areas in the north of China. The content of polysaccharide is about 20% in Artemisia sphaerocephala seed. It can absorb 60 times water as the weight of itself, with the high viscosity, which is 1800 times that of gelatin, can be applied widely in different fields, such as chemical industry, food industry and ecology. Artemisia sphaerocephala polysaccharide (ASP) can reduce hyperglycemia, change glucose into glycogen; recover the destructed pancreatic cell, enhance the physical antioxidant function; decrease glutamic oxaloacetic transminase (GOT), glutamic pyruvic transaminase (GPT), blood urea nitrogen (BUN) in blood and protect the hepar and kidney, see China patent ZL200510002228.5.
The most conventional method for extraction of ASP from Artemisia sphaerocephala is hot water extraction. The disadvantages of the methods are: time-consuming, higher energy consumption, lower polysaccharide yield and high cost.
The main advantages of microwave-assisted extraction are the considerable reduction in time and solvent as compared to conventional techniques. Microwave technique is a kind of environment-friendly, green manufacturing technology which generate 2.45 billion times/s of ultra-high frequency concussion. Microwave energy penetrates materials and produces a volumetrically distributed heat source due to molecular friction resulting from dipolar rotation of polar solvents and from the conductive migration of dissolved ions. The highly localized temperature and pressure can cause selective migration of target compounds from the material to the extraction solvent at a more rapid rate and with similar or better recoveries compared with conventional heat-flux extraction.
Microwave-assisted extraction technique is developed for the extraction of polysaccharide and polyphenolic compounds from green tea. The yield of polysaccharide was 30%-45% with the microwave power of 500 W-1500 W, see China patent CN 1107075C. Astragalus polysaccharide is extracted with the polysaccharide yield of 9%-20% by microwave-assisted method (microwave power of 200 W), see China patent CN 1880342A. China patent CN 1246320 C describes a microwave-assisted extraction method of matrine which have the content of 0.22%. The microwave intensity is 12-36 W/L in the appearance of polarity organic solvent. Ginkgo flavone and ginkgolide are extracted using microwave-assisted method in organic solvent/water mixture at the microwave power of 500 W-1500 W. The yields of ginkgo flavone and ginkgolide are 38%-40% and 10%-12%, respectively, see China patent CN 1109028C. The effective components are extracted from glycyrrhiza with microwave-assisted method. The yield of crude extract is about 20% in the microwave intensity of 30-70 W/g, see China patent CN 128764C.
So far, no literatures or patents refer to microwave-assistant extraction of natural polysaccharide from discarded Artemisia sphaerocephala seed de-oiling dregs.